1. Field of the Invention
The present invention relates to a sheath device for an endoscope, which is fitted over an insert tube of the endoscope when used for an endoscopic procedure and which can be removed and disposed of after use, to prevent the transmission of bacteria or viruses from one patient to another through the endoscope.
More particularly, the present invention relates to a sheath device for an endoscope, wherein a sheath, which comprises the device, is inflated with air so that the insert tube of the endoscope is smoothly inserted into and removed from the sheath which is in an inflated state.
This type of sheath device is provided with a sheath cover as being an auxiliary member which allows the sheath to inflate to a configuration that is the most suitable for insertion and removal of the insert tube of the endoscope, and which also prevents bursting of the sheath due to overinflation. This sheath cover also serves to isolate the sheath from the external environment when the sheath, which is contaminated during an endoscopic procedure, is drawn out of a hollow organ of the patient's body.
2. Description of the Prior Art
In the conventional sheath device for an endoscope, as shown in FIG. 5A, a sheath cover 101 is formed from a straight cylindrical member that has a uniform inner diameter, and it is designed to allow a sheath 102 to inflate until the outer diameter of the sheath 102 becomes equal to the inner diameter of the sheath cover 101. Air that is used to inflate the sheath 102 is sent into the sheath 102 through an air supply tube (not shown) that is connected to an external air supply pump.
However, since the sheath cover 101 has a uniform inner diameter, when the sheath 102 is inflated inside the sheath cover 101, it inflates radially and also expands along the longitudinal axis. In consequence, when the sheath 102 comes into contact with the sheath cover 101, an extra portion of the sheath 102, which expands in the longitudinal direction, is curled at the distal end of the sheath 102, as shown in FIG. 5B.
As the air is released from the sheath 102 after the supply of air into the sheath 102 has been suspended, the diameter of the sheath 102 decreases. In consequence, the sheath 102 is fitted over the insert tube of the endoscope with the curled portion being left as it is, as shown in FIG. 5C. In such a case, the endoscope cannot be used for an endoscopic procedure in a hollow organ of the patient's body.
In addition, since the amount and pressure of air that are needed to inflate the sheath depend on the type of sheath device employed, it is very difficult to control the air pressure with accuracy in accordance with each individual type of sheath device. If the air pressure cannot effectively be controlled, the sheath may burst due to the oversupply of air. If the sheath or the sheath cover bursts when the sheath is removed after an endoscopic procedure, there is a danger of infection with pathogens which are scattered around from the endoscope.